Cytotoxicity comparison on different parts of three Digitalis species and isolation of potential bioactive compounds

Abstract

In the Flora of Turkey, the genus Digitalis is represented by nine species [1]. Digitalis species contain biologically active compounds such as cardenolides, phenylethanoid glycosides, flavonoids, and anthraquinones. In this research three Digitalis species [Plantaginaceae]; D. davisiana Heywood, D. grandiflora Miller and D. viridiflora Lindley were studied in the point of cytotoxicity. To determine the bioactive part of the plant, root and aerial parts were extracted with methanol separately. Cytotoxic activity was performed by MTT method through 2 cancer cell lines HEp-2 (Human larynx epidermoid carcinoma), HepG2 (Human hepatocelular carcinoma) and a non-cancerous cell line 3Y1 (rat fibroblast cell) [2]. Methanol extracts of the aerial parts and the roots of three plants were used for cytotoxic activity tests. It was found that these three plants have different potentials for cytotoxicity. Aerial parts were found to be more active than the roots on tested cancer cell lines. In addition to this, D. davisiana aerial parts extract (DD-APE) was found to be the most active among all. IC50 values of DD-APE were 50.8, 211.4 and 94.7 µg/mL respectively for HEp-2, HepG2 and 3Y1 cell lines. The tested extracts are more cytotoxic on HEp-2 cell line than HepG2 and 3Y1 cell lines. This selectivity is important for the discovery of new anticancer agents. After evaluating the bioactivity test results, isolation studies started from active, phenylethanoid glycosides rich fractions. Repeated column chromatography studies resulted in the isolation of five phenylethanoid glycosides. Deacyllugrandoside (1), lugrandoside (2), isolugrandoside (3), maxoside (4) and 3,4-dihydroxy-β-phenylethoxy-O-[β-glucopyranosyl-(1→3)]-O-[α-rhamnopyranosyl-(1→6)]-4-O-(E)-feruloyl-β-glucopyranoside (5) were identified by extensive NMR techniques. Isolation and cytotoxic activity studies on isolated compounds are still in progress.